/*
 * Copyright 2002-2018 the original author or authors.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *      https://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package org.springframework.web.multipart.commons;

import org.apache.commons.fileupload.*;
import org.apache.commons.fileupload.servlet.ServletFileUpload;
import org.springframework.util.Assert;
import org.springframework.web.context.ServletContextAware;
import org.springframework.web.multipart.MaxUploadSizeExceededException;
import org.springframework.web.multipart.MultipartException;
import org.springframework.web.multipart.MultipartHttpServletRequest;
import org.springframework.web.multipart.MultipartResolver;
import org.springframework.web.multipart.support.AbstractMultipartHttpServletRequest;
import org.springframework.web.multipart.support.DefaultMultipartHttpServletRequest;
import org.springframework.web.util.WebUtils;

import javax.servlet.ServletContext;
import javax.servlet.http.HttpServletRequest;
import java.util.List;

/**
 * Servlet-based {@link MultipartResolver} implementation for
 * <a href="https://commons.apache.org/proper/commons-fileupload">Apache Commons FileUpload</a>
 * 1.2 or above.
 *
 * <p>Provides "maxUploadSize", "maxInMemorySize" and "defaultEncoding" settings as
 * bean properties (inherited from {@link CommonsFileUploadSupport}). See corresponding
 * ServletFileUpload / DiskFileItemFactory properties ("sizeMax", "sizeThreshold",
 * "headerEncoding") for details in terms of defaults and accepted values.
 *
 * <p>Saves temporary files to the servlet container's temporary directory.
 * Needs to be initialized <i>either</i> by an application context <i>or</i>
 * via the constructor that takes a ServletContext (for standalone usage).
 *
 * @author Trevor D. Cook
 * @author Juergen Hoeller
 * @see #CommonsMultipartResolver(ServletContext)
 * @see #setResolveLazily
 * @see org.apache.commons.fileupload.servlet.ServletFileUpload
 * @see org.apache.commons.fileupload.disk.DiskFileItemFactory
 * @since 29.09.2003
 */
public class CommonsMultipartResolver extends CommonsFileUploadSupport
        implements MultipartResolver, ServletContextAware {

    private boolean resolveLazily = false;


    /**
     * Constructor for use as bean. Determines the servlet container's
     * temporary directory via the ServletContext passed in as through the
     * ServletContextAware interface (typically by a WebApplicationContext).
     *
     * @see #setServletContext
     * @see org.springframework.web.context.ServletContextAware
     * @see org.springframework.web.context.WebApplicationContext
     */
    public CommonsMultipartResolver() {
        super();
    }

    /**
     * Constructor for standalone usage. Determines the servlet container's
     * temporary directory via the given ServletContext.
     *
     * @param servletContext the ServletContext to use
     */
    public CommonsMultipartResolver(ServletContext servletContext) {
        this();
        setServletContext(servletContext);
    }


    /**
     * Set whether to resolve the multipart request lazily at the time of
     * file or parameter access.
     * <p>Default is "false", resolving the multipart elements immediately, throwing
     * corresponding exceptions at the time of the {@link #resolveMultipart} call.
     * Switch this to "true" for lazy multipart parsing, throwing parse exceptions
     * once the application attempts to obtain multipart files or parameters.
     */
    public void setResolveLazily(boolean resolveLazily) {
        this.resolveLazily = resolveLazily;
    }

    /**
     * Initialize the underlying {@code org.apache.commons.fileupload.servlet.ServletFileUpload}
     * instance. Can be overridden to use a custom subclass, e.g. for testing purposes.
     *
     * @param fileItemFactory the Commons FileItemFactory to use
     * @return the new ServletFileUpload instance
     */
    @Override
    protected FileUpload newFileUpload(FileItemFactory fileItemFactory) {
        return new ServletFileUpload(fileItemFactory);
    }

    @Override
    public void setServletContext(ServletContext servletContext) {
        if (!isUploadTempDirSpecified()) {
            getFileItemFactory().setRepository(WebUtils.getTempDir(servletContext));
        }
    }


    @Override
    public boolean isMultipart(HttpServletRequest request) {
        return ServletFileUpload.isMultipartContent(request);
    }

    @Override
    public MultipartHttpServletRequest resolveMultipart(final HttpServletRequest request) throws MultipartException {
        Assert.notNull(request, "Request must not be null");
        if (this.resolveLazily) {
            return new DefaultMultipartHttpServletRequest(request) {
                @Override
                protected void initializeMultipart() {
                    MultipartParsingResult parsingResult = parseRequest(request);
                    setMultipartFiles(parsingResult.getMultipartFiles());
                    setMultipartParameters(parsingResult.getMultipartParameters());
                    setMultipartParameterContentTypes(parsingResult.getMultipartParameterContentTypes());
                }
            };
        }
        else {
            MultipartParsingResult parsingResult = parseRequest(request);
            return new DefaultMultipartHttpServletRequest(request, parsingResult.getMultipartFiles(),
                    parsingResult.getMultipartParameters(), parsingResult.getMultipartParameterContentTypes());
        }
    }

    /**
     * Parse the given servlet request, resolving its multipart elements.
     *
     * @param request the request to parse
     * @return the parsing result
     * @throws MultipartException if multipart resolution failed.
     */
    protected MultipartParsingResult parseRequest(HttpServletRequest request) throws MultipartException {
        String encoding = determineEncoding(request);
        FileUpload fileUpload = prepareFileUpload(encoding);
        try {
            List<FileItem> fileItems = ((ServletFileUpload) fileUpload).parseRequest(request);
            return parseFileItems(fileItems, encoding);
        }
        catch (FileUploadBase.SizeLimitExceededException ex) {
            throw new MaxUploadSizeExceededException(fileUpload.getSizeMax(), ex);
        }
        catch (FileUploadBase.FileSizeLimitExceededException ex) {
            throw new MaxUploadSizeExceededException(fileUpload.getFileSizeMax(), ex);
        }
        catch (FileUploadException ex) {
            throw new MultipartException("Failed to parse multipart servlet request", ex);
        }
    }

    /**
     * Determine the encoding for the given request.
     * Can be overridden in subclasses.
     * <p>The default implementation checks the request encoding,
     * falling back to the default encoding specified for this resolver.
     *
     * @param request current HTTP request
     * @return the encoding for the request (never {@code null})
     * @see javax.servlet.ServletRequest#getCharacterEncoding
     * @see #setDefaultEncoding
     */
    protected String determineEncoding(HttpServletRequest request) {
        String encoding = request.getCharacterEncoding();
        if (encoding == null) {
            encoding = getDefaultEncoding();
        }
        return encoding;
    }

    @Override
    public void cleanupMultipart(MultipartHttpServletRequest request) {
        if (!(request instanceof AbstractMultipartHttpServletRequest) ||
                ((AbstractMultipartHttpServletRequest) request).isResolved()) {
            try {
                cleanupFileItems(request.getMultiFileMap());
            }
            catch (Throwable ex) {
                logger.warn("Failed to perform multipart cleanup for servlet request", ex);
            }
        }
    }

}
